1. Field of the Invention
The present invention relates to a process of curving a casing of stretched plastic material, which casing is filled with a fluid such as gas or air, curved, heated and subsequently cooled down in its curved position.
The present invention further relates to apparatus for performing the above process.
2. Description of the Prior Art
In the prior art a process has been used by means of which a casing is wound under tension about a smooth, heated mandrel, in order to obtain the desired curve.
The difficulty with said known process is that casing portions, cut off from said casing, have to be filled with a fluid, such as air or gas, prior to curving them. Moreover, the tension with which said casing has to be wound about a mandrel (with respect to the temperature of the latter) is subject to very restricted limits.
So as to curve casings for, for example, sausages, a thinwalled tube of stretched plastic material is curved, and subsequently round sausages, to wit sausages comprising adjacent or almost adjacent extremities, are made from said material. Curving the thinwalled tubes should be performed in a very accurate manner, since proper attention has to be paid to a careful control of the condition of the inner curve, as the inner curved part of casings should be entirely smooth; therefore any crimpling of the relative casing should be avoided during the respective process.